Hitherto, organic acids or their salts and glycol series pastes have been principally used as an electrolyte for electrolytic capacitors for general purposes. The latest increase in their utilization in connection with electronic instruments requires improved reliability and performance from the capacitor in the, but this has hindered by the problem of the presence of water in the paste and consequently an electrolytic using an aprotic solvent in place of organic acid and its salt and glycol paste has begun to receive attention.
The greatest subject of employment of the aprotic solvent system electrolyte is how to obtain an electrolyte of high conductivity and to achieve this an organic carboxylic acid or its salt which is well soluble in the aprotic solvent and has a high degree of dissociation has been extensively researched, but without success. To solve this problem and obtain a high conductivity a solvent which produces water as a result of the reaction between acids and alcohols or glycols and even water is incorporated into the aprotic solvent but with still insufficient conductivity, increments of water, and solute contents with poor reliability at the elevated temperature, as disclosed in the Japanese patent publications Nos. 55-3989, 57-56763, 58-32769 and the U.S. Pat. No. 4,117,531.
After extensive researches and studies to obtain an electrolyte which is a substantially nonaqueous system electrolyte and which has a high conductivity with use of an aprotic solvent but without using any solvent which forms water in reaction between acids and alcohols with glycols, it has been discovered that a N-heterocyclic compound salt of fluorocomplex acid has a high solubility in the aprotic solvent with an enhanced releasability and provides a high conductivity.